Load balancing

ABSTRACT

A method of communicating in a wireless network including receiving effective load values for sectors accessible to an access terminal of the wireless network. The effective load values represent effective loads on the sectors. The method also includes receiving pilot signal channel quality values of the sectors and selecting a serving sector, for the access terminal based on the effective load values and the pilot signal channel quality values.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 U.S.C. §119(e) to U.S.Provisional Patent Application No. 61/358,539 entitled Load Balancing InWireless Networks, filed on Jun. 25, 2010, the disclosure of which isexpressly incorporated by reference herein in its entirety.

BACKGROUND

1. Field

Aspects of the present disclosure relate generally to wirelesscommunication systems, and more particularly to load balancing inwireless networks, such as EVDO, HSPA and LTE networks.

2. Background

Wireless communication networks are widely deployed to provide variouscommunication services such as voice, video, packet data, messaging,broadcast, etc. These wireless networks may be multiple-access networkscapable of supporting multiple users by sharing the available networkresources. Examples of such multiple-access networks include CodeDivision Multiple Access (CDMA) networks, Time Division Multiple Access(TDMA) networks, Frequency Division Multiple Access (FDMA) networks,Orthogonal FDMA (OFDMA) networks, and Single-Carrier FDMA (SC-FDMA)networks.

A wireless communication network may include a number of base stationsthat can support communication for a number of user equipments (UEs) orAccess Terminals (AT). The UEs or ATs may be dispersed throughout thenetwork. Each base station may serve one or more UEs or ATs at any givenmoment. A UE or AT may communicate with a base station via the downlinkand uplink. The downlink (or forward link) refers to the communicationlink from the base station to the UE or AT, and the uplink (or reverselink) refers to the communication link from the UE or AT to the basestation.

A base station may transmit data and control information on the downlinkto a UE or AT and/or may receive data and control information on theuplink from the UE or AT. On the downlink, a transmission from the basestation may encounter interference due to transmissions from neighborbase stations or from other wireless radio frequency (RF) transmitters.On the uplink, a transmission from the UE or AT may encounterinterference from uplink transmissions of other UEs or ATs communicatingwith the neighbor base stations or from other wireless RF transmitters.This interference may degrade performance on both the downlink anduplink.

Moreover, although heavily loaded sectors may have lightly loadedneighbors, current server selection solutions usually do not considerthe load of neighbor cells. Rather, current solutions are based onpurely downlink channel quality.

As the demand for mobile broadband access continues to increase, thepossibilities of interference and congested networks grows with more UEsor ATs accessing the long-range wireless communication networks and moreshort-range wireless systems being deployed in communities. Research anddevelopment continue to advance the UMTS technologies not only to meetthe growing demand for mobile broadband access, but to advance andenhance the user experience with mobile communications.

SUMMARY

According to some aspects of the disclosure, a method of communicatingin a wireless network includes receiving effective load values forsectors accessible to an access terminal of the wireless network. Theeffective load values may represent effective loads on the sectors. Themethod may also include receiving pilot signal channel quality values ofthe sectors and selecting a serving sector, from the sectors, for theaccess terminal based on the effective load values and the pilot signalchannel quality values.

According to some aspects of the disclosure, a method of communicatingin a wireless network includes receiving effective load values at anaccess terminal for accessible sectors of the wireless network. Theeffective load values may represent effective loads on the sectors. Themethod may also include identifying pilot signal channel quality valuesof the accessible sectors. The method may also include selecting aserving sector, from the accessible sectors, for the access terminalbased on the effective load values and the pilot signal channel qualityvalues.

According to some aspects of the disclosure, an apparatus forcommunicating in a wireless network includes means for receivingeffective load values for sectors accessible to an access terminal ofthe wireless network. The effective load values may represent effectiveloads on the sectors. The apparatus may also include means for receivingpilot signal channel quality values of the sectors. The apparatus mayfurther include means for selecting a serving sector, from the sectors,for the access terminal based on the effective load values and the pilotsignal channel quality values.

According to some aspects of the disclosure, an apparatus forcommunicating in a wireless network includes means for receivingeffective load values at an access terminal for accessible sectors ofthe wireless network. The effective load values may represent effectiveloads on the sectors. The apparatus may also include means foridentifying pilot signal channel quality values of the accessiblesectors. The apparatus may further include means for selecting a servingsector, from the accessible sectors, for the access terminal based onthe effective load values and the pilot signal channel quality values.

According to some aspects of the disclosure, an apparatus forcommunicating in a wireless network includes a memory and at least oneprocessor coupled to the memory. The processor(s) is configured toreceive effective load values for sectors accessible to an accessterminal of the wireless network. The effective load values mayrepresent effective loads on the sectors. The processor(s) is furtherconfigured to receive pilot signal channel quality values of thesectors. The processor(s) may also be configured to select a servingsector, from the sectors, for the access terminal based on the effectiveload values and the pilot signal channel quality values.

According to some aspects of the disclosure, an apparatus forcommunicating in a wireless network includes a memory and at least oneprocessor coupled to the memory. The processor(s) is configured toreceive effective load values at an access terminal for accessiblesectors of the wireless network. The effective load values may representeffective loads on the sectors. The processor(s) is further configuredto identify pilot signal channel quality values of the accessiblesectors. The processor(s) may also be configured to select a servingsector, from the accessible sectors, for the access terminal based onthe effective load values and the pilot signal channel quality values.

According to some aspects of the disclosure, a computer program productfor wireless communications in a wireless network includes acomputer-readable medium having non-transitory program code recordedthereon. The program code includes program code to receive effectiveload values for sectors accessible to an access terminal of the wirelessnetwork. The effective load values may represent effective loads on thesectors. The program code also includes program code to receive pilotsignal channel quality values of the sectors. The program code may alsoinclude program code to select a serving sector, from the sectors, forthe access terminal based on the effective load values and the pilotsignal channel quality values.

According to some aspects of the disclosure, a computer program productfor wireless communications in a wireless network includes acomputer-readable medium having non-transitory program code recordedthereon. The program code includes program code to receive effectiveload values at an access terminal for accessible sectors of the wirelessnetwork. The effective load values may represent effective loads on thesectors. The program code also includes program code to identify pilotsignal channel quality values of the accessible sectors. The programcode may also include program code to select a serving sector, from theaccessible sectors, for the access terminal based on the effective loadvalues and the pilot signal channel quality values.

This has outlined, rather broadly, the features and technical advantagesof the present disclosure in order that the detailed description thatfollows may be better understood. Additional features and advantages ofthe disclosure will be described below. It should be appreciated bythose skilled in the art that this disclosure may be readily utilized asa basis for modifying or designing other structures for carrying out thesame purposes of the present disclosure. It should also be realized bythose skilled in the art that such equivalent constructions do notdepart from the teachings of the disclosure as set forth in the appendedclaims. The novel features, which are believed to be characteristic ofthe disclosure, both as to its organization and method of operation,together with further objects and advantages, will be better understoodfrom the following description when considered in connection with theaccompanying figures. It is to be expressly understood, however, thateach of the figures is provided for the purpose of illustration anddescription only and is not intended as a definition of the limits ofthe present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, nature, and advantages of the present disclosure willbecome more apparent from the detailed description set forth below whentaken in conjunction with the drawings in which like referencecharacters identify correspondingly throughout.

FIG. 1 is a block diagram conceptually illustrating an example of atelecommunications system.

FIG. 2 is a block diagram illustrating a method for load balancing in awireless network.

FIG. 3 is a block diagram illustrating a method for communicating in awireless network.

FIG. 4 is a block diagram conceptually illustrating a design of a basestation/eNodeB and a UE configured according to one aspect of thepresent disclosure.

FIG. 5 shows an exemplary wireless communication system according tosome aspects of the disclosure.

FIG. 6 illustrates when effective load metric of a sector carrier istransported from a base station controller from a base stationtransceiver according to some aspects of the disclosure.

DETAILED DESCRIPTION

The detailed description set forth below, in connection with theappended drawings, is intended as a description of variousconfigurations and is not intended to represent the only configurationsin which the concepts described herein may be practiced. The detaileddescription includes specific details for the purpose of providing athorough understanding of the various concepts. However, it will beapparent to those skilled in the art that these concepts may bepracticed without these specific details. In some instances, well-knownstructures and components are shown in block diagram form in order toavoid obscuring such concepts.

The techniques described herein may be used for various wirelesscommunication networks such as Code Division Multiple Access (CDMA)networks, Time Division Multiple Access (TDMA) networks, FrequencyDivision Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA)networks, Single-Carrier FDMA (SC-FDMA) networks, etc. The terms“networks” and “systems” are often used interchangeably. A CDMA networkmay implement a radio technology such as Universal Terrestrial RadioAccess (UTRA), CDMA2000, etc. UTRA includes Wideband-CDMA (W-CDMA) andLow Chip Rate (LCR). CDMA2000 covers IS-2000, IS-95 and IS-856standards. IS-856 is commonly referred to as 1xEV-DO, high rate packetdata (HRPD), etc. Evolution Data Optimized (EV-DO) is atelecommunications standard promulgated by the 3^(rd) GenerationPartnership Project 2 as part of the CDMA2000 family. EV-DO facilitateshigh data rates in wireless networks. EV-DO has gone through severalevolutions, of which some revisions provide for a forward link usingTime Division Multiple Access (TDMA) principles to transmit datasub-streams on multiple carriers (tones).

A TDMA network may implement a radio technology such as Global Systemfor Mobile Communications (GSM). An OFDMA network may implement a radiotechnology such as Evolved UTRA (E-UTRA), IEEE 802.11, IEEE 802.16, IEEE802.20, Flash-OFDM®, etc. UTRA, E-UTRA, and GSM are part of UniversalMobile Telecommunication System (UMTS). Long Term Evolution (LTE) is anupcoming release of UMTS that uses E-UTRA. UTRA, E-UTRA, GSM, UMTS andLTE are described in documents from an organization named “3rdGeneration Partnership Project” (3GPP). CDMA2000 is described indocuments from an organization named “3rd Generation Partnership Project2” (3GPP2). These various radio technologies and standards are known inthe art. For clarity, certain aspects of the techniques are describedbelow for LTE, and LTE terminology is used in much of the descriptionbelow.

FIG. 1 shows a wireless communication network 100, which may be an LTE-Anetwork, in which load balancing may be implemented. The wirelessnetwork 100 includes a number of evolved node Bs (eNodeBs) 110 and othernetwork entities. An eNodeB may be a station that communicates with theUEs and may also be referred to as a base station, base transceiverstation (BTS) a node B, a base station controller (BSC), an accesspoint, and the like. Each eNodeB 110 may provide communication coveragefor a particular geographic area. In 3GPP, the term “cell” can refer tothis particular geographic coverage area of an eNodeB and/or an eNodeBsubsystem serving the coverage area, depending on the context in whichthe term is used.

To improve system capacity, the overall coverage area of a base stationor eNodeB may be partitioned into multiple (e.g., three) smaller areas.Each smaller area may be served by a respective base station subsystem.In 3GPP, the term “cell” can refer to the smallest coverage area of abase station and/or a base station subsystem serving this coverage area.In 3GPP2, the term “sector” or “cell-sector” can refer to the smallestcoverage area of a base station and/or a base station subsystem servingthis coverage area. For clarity, 3GPP2 concept of “sector” is used inthe description below. A base station may support one or multiple (e.g.,three) sectors.

An eNodeB may provide communication coverage for a macro cell, a picocell, a femto cell, and/or other types of cell. A macro cell generallycovers a relatively large geographic area (e.g., several kilometers inradius) and may allow unrestricted access by UEs with servicesubscriptions with the network provider. A pico cell would generallycover a relatively smaller geographic area and may allow unrestrictedaccess by UEs with service subscriptions with the network provider. Afemto cell would also generally cover a relatively small geographic area(e.g., a home) and, in addition to unrestricted access, may also providerestricted access by UEs having an association with the femto cell(e.g., UEs in a closed subscriber group (CSG), UEs for users in thehome, and the like). An eNodeB for a macro cell may be referred to as amacro eNodeB. An eNodeB for a pico cell may be referred to as a picoeNodeB. In addition, an eNodeB for a femto cell may be referred to as afemto eNodeB or a home eNodeB. In the example shown in FIG. 1, theeNodeBs 110 a, 110 b and 110 c are macro eNodeBs for the macro cells 102a, 102 b and 102 c, respectively. The eNodeB 110 x is a pico eNodeB fora pico cell 102 x. In addition, the eNodeBs 110 y and 110 z are femtoeNodeBs for the femto cells 102 y and 102 z, respectively. An eNodeB maysupport one or multiple (e.g., two, three, four, and the like) cells.

The wireless network 100 may also include relay stations. A relaystation is a station that receives a transmission of data and/or otherinformation from an upstream station (e.g., an eNodeB, UE, etc.) andsends a transmission of the data and/or other information to adownstream station (e.g., a UE or an eNodeB). A relay station may alsobe a UE that relays transmissions for other UEs. In the example shown inFIG. 1, a relay station 110 r may communicate with the eNodeB 110 a anda UE 120 r in order to facilitate communication between the eNodeB 110 aand the UE 120 r. A relay station may also be referred to as a relayeNodeB, a relay, etc.

The wireless network 100 may be a heterogeneous network that includeseNodeBs of different types, e.g., macro eNodeBs, pico eNodeBs, femtoeNodeBs, relays, etc. These different types of eNodeBs may havedifferent transmit power levels, different coverage areas, and differentimpact on interference in the wireless network 100. For example, macroeNodeBs may have a high transmit power level (e.g., 20 Watts) whereaspico eNodeBs, femto eNodeBs and relays may have a lower transmit powerlevel (e.g., 1 Watt).

A network controller 130 may couple to a set of eNodeBs 110 and providecoordination and control for these eNodeBs 110. The network controller130 may communicate with the eNodeBs 110 via a backhaul. The eNodeBs 110may also communicate with one another, e.g., directly or indirectly viaa wireless backhaul or a wireline backhaul.

The UEs 120 are dispersed throughout the wireless network 100, and eachUE may be stationary or mobile. A UE may also be referred to as aterminal, a mobile station, a subscriber unit, an access terminal (AT),a station, or the like. A UE may be a cellular phone, a personal digitalassistant (PDA), a wireless modem, a wireless communication device, ahandheld device, a laptop computer, a cordless phone, a wireless localloop (WLL) station, a tablet, or the like. A UE may be able tocommunicate with macro eNodeBs, pico eNodeBs, femto eNodeBs, relays, andthe like. In FIG. 1, a solid line with double arrows indicates desiredtransmissions between a UE and a serving eNodeB, which is an eNodeBdesignated to serve the UE on the downlink and/or uplink. A dashed linewith double arrows indicates interfering transmissions between a UE andan eNodeB.

FIG. 4 shows a block diagram of a design of a base station/eNodeB 110and a UE 120, which may be one of the base stations/eNodeBs and one ofthe UEs in FIG. 1. The base station 110 may be the macro eNodeB 110 c inFIG. 1, and the UE 120 may be the UE 120 y. The base station 110 mayalso be a base station of some other type. The base station 110 may beequipped with antennas 434 a through 434 t, and the UE 120 may beequipped with antennas 452 a through 452 r.

At the base station 110, a transmit processor 420 may receive data froma data source 412 and control information from a controller/processor440. The control information may be for the PBCH, PCFICH, PHICH, PDCCH,etc. The data may be for the PDSCH, etc. The processor 420 may process(e.g., encode and symbol map) the data and control information to obtaindata symbols and control symbols, respectively. The processor 420 mayalso generate reference symbols, e.g., for the PSS, SSS, andcell-specific reference signal. A transmit (TX) multiple-inputmultiple-output (MIMO) processor 430 may perform spatial processing(e.g., precoding) on the data symbols, the control symbols, and/or thereference symbols, if applicable, and may provide output symbol streamsto the modulators (MODs) 432 a through 432 t. Each modulator 432 mayprocess a respective output symbol stream (e.g., for OFDM, etc.) toobtain an output sample stream. Each modulator 432 may further process(e.g., convert to analog, amplify, filter, and upconvert) the outputsample stream to obtain a downlink signal. Downlink signals frommodulators 432 a through 432 t may be transmitted via the antennas 434 athrough 434 t, respectively.

At the UE 120, the antennas 452 a through 452 r may receive the downlinksignals from the base station 110 and may provide received signals tothe demodulators (DEMODs) 454 a through 454 r, respectively. Eachdemodulator 454 may condition (e.g., filter, amplify, downconvert, anddigitize) a respective received signal to obtain input samples. Eachdemodulator 454 may further process the input samples (e.g., for OFDM,etc.) to obtain received symbols. A MIMO detector 456 may obtainreceived symbols from all the demodulators 454 a through 454 r, performMIMO detection on the received symbols if applicable, and providedetected symbols. A receive processor 458 may process (e.g., demodulate,deinterleave, and decode) the detected symbols, provide decoded data forthe UE 120 to a data sink 460, and provide decoded control informationto a controller/processor 480.

On the uplink, at the UE 120, a transmit processor 464 may receive andprocess data (e.g., for the PUSCH) from a data source 462 and controlinformation (e.g., for the PUCCH) from the controller/processor 480. Theprocessor 464 may also generate reference symbols for a referencesignal. The symbols from the transmit processor 464 may be precoded by aTX MIMO processor 466 if applicable, further processed by the modulators454 a through 454 r (e.g., for SC-FDM, etc.), and transmitted to thebase station 110. At the base station 110, the uplink signals from theUE 120 may be received by the antennas 434, processed by thedemodulators 432, detected by a MIMO detector 436 if applicable, andfurther processed by a receive processor 438 to obtain decoded data andcontrol information sent by the UE 120. The processor 438 may providethe decoded data to a data sink 439 and the decoded control informationto the controller/processor 440. The base station 110 can send messagesto other base stations, for example, over an X2 interface 441.

The controllers/processors 440 and 480 may direct the operation at thebase station 110 and the UE 120, respectively. The processor 440 and/orother processors and modules at the base station 110 may perform ordirect the execution of various processes for the techniques describedherein. The processors 440, 480 and/or other processors and modules atthe UE 120 and eNodeB 110 may also perform or direct the execution ofthe functional blocks illustrated in the method flow charts of FIGS. 2and 3, and/or other processes for the techniques described herein. Thememories 442 and 482 may store data and program codes for the basestation 110 and the UE 120, respectively. A scheduler 444 may scheduleUEs for data transmission on the downlink and/or uplink.

FIG. 5 shows an exemplary wireless communication system 500 according tosome aspects of the disclosure for an EVDO network, rather than an LTEnetwork. For purposes of illustration, FIG. 5 shows remote units (orATs) 520, base transceiver stations (BTSs)/base stations 510, and a basestation controller (or BSC) 530. It will be recognized that wirelesscommunication systems may have many more remote units BTSs and basestations controllers. The remote units 520 may be, for example, personaldigital assistants (PDAs), smartphones, cellular phones, laptopcomputers, netbook computers, desktop computers, media extender devices,tablets, and media set top boxes, which in various aspects providefunctionality for incorporating techniques into wireless broadbandtechnology, such as Evolution Data optimized (EVDO), as discussedfurther below. The functionality described in more detail below can beimplemented using executable code stored to a computer-readable mediumintegral to, or separate from, the remote units 520. FIG. 5 shows theforward link signals 580 from the base stations 510 and the remote units520 and the reverse link signals 590 from the remote units 520 to thebase stations 510.

The BSC 530 and/or other processors and modules at the BSC 530. mayperform or direct the execution of various processes for the techniquesdescribed herein. The AT 520, BTS 510, BSC 530 and included processorsand modules may also perform or direct the execution of the functionalblocks illustrated in the method flow chart of FIGS. 2 and 3, and/orother processes for the techniques described herein.

Furthermore, the examples below specifically refer to components in anEVDO network, but the scope of aspects is not so limited. For instance,many of the features described below are adaptable for use in systemsother than EVDO systems, such as systems using Universal MobileTelecommunications System (UMTS), Global System for MobileCommunications/Enhanced Data Rates for GSM Evolution (GSM/EDGE), LongTerm Evolution (LTE), LTE-Advanced and the like.

Load Balancing

Network load balancing (NLB) techniques or processes for performingserver selection to balance the load of sectors in a wirelesscommunication system are described. Server selection refers to a processto select a serving sector or cell for a terminal or access terminal(AT). In some aspects, the load balancing processes may be implementedon EV-DO revisions such as A, B, Rel0 and DO-Advanced network, althoughthe process is equally applicable to other networks such as HSPA and LTE(e.g., single and multi-carrier LTE). Although single-carrier devicesand networks are described, multi-carrier devices and networks may alsoemploy the exemplary aspects disclosed herein.

As previously described above, the ATs may be distributed throughout thesystem or network, and each sector may have any number of ATs within itscoverage. Some sectors may include many ATs and may be more heavilyloaded whereas some other sectors may include few ATs and may be lightlyloaded. In many instances, a heavily loaded sector may be adjacent to(e.g., surrounded by) one or more lightly loaded sectors.

In some aspects, network load balancing may be performed to move ATsfrom a heavily loaded sector to a lightly loaded sector in order toimprove performance for all affected ATs as well as the system. Networkload balancing may be performed based on various designs, which may bedependent on the signaling messages available to send server selectioninformation to ATs, whether server selection is performed by the ATs orUEs (i.e., device-driven) or a network entity, e.g., eNodeB 110, BTS 510or base station controller 530 (i.e., network induced), and/or otherfactors.

If an uplink-downlink imbalance is created by network load balancing(NLB), it may be addressed by adjusting the gains of uplink channels.When network load balancing processes are implemented at the networklevel (eNodeB, BSC and BTS) and at the access terminal (AT) or UE level,the AT could potentially not be served by the cell/sector with thestrongest downlink pilot when it is in the network load balancing modedescribed here. The chosen downlink may be weaker in signal strength,and a symmetric uplink to that cell/sector may be correspondingly weakas well. To account for the correspondingly weak uplink, gains of uplinkchannels that the AT uses to send signals related to serving sector/cellselection, as well as any feedback for transmissions from the selectedserving sector/cell, may be boosted to reach the new desired servingsector/cell.

In some aspects, it may be desirable to implement a network induced ordriven network load balancing under the following conditions amongothers:

-   -   When a base station controller (BSC) determines that the AT has        no Delay Sensitive flows, only Throughput Sensitive flows, on        the carriers that network load balancing is to be performed.    -   When a BSC determines that the AT is in soft-handoff with        multiple cells on the carriers under consideration for network        load balancing and it has one sector in each cell that it can        potentially receive service from at the current time on those        carriers.    -   When the BSC determines that a multi-carrier AT can receive        service from different cells/sectors on different carriers,        i.e., it is not constrained to receive service from the same        cell/sector on all carriers.    -   When the BSC determines that the AT does not support receiving        an indication from the network containing relative sector load        information for use by the AT for load balancing.    -   When the BSC determines that the AT can be requested to update        the network with the most current Signal to Noise Ratios for the        pilots transmitted by the sectors that the AT can receive        service from.

In some aspects, server selection may be performed based on metrics suchas an effective load (N_(eff)) on a sector carrier seen by an incomingthroughput-sensitive (TS) flow and based on active ATs in a sector andtheir pilot strengths or pilot signal channel quality values. Themetrics are the inputs for the network load balancing process. TheN_(eff) metric may capture or account for considerations such as numberof existing throughput-sensitive-flows in the sector-carrier thatcompete for scheduler resources such as time, frequency, etc. (e.g.,they have data to transmit in BTS buffers). The N_(eff) metric may alsotake into consideration, scheduler resources that are available, thatare normalized for any reserved scheduler resources in the sector (e.g.,resources reserved for control channels, etc.). For example, if “n”scheduler time units out of “m” within a cycle are reserved, apply anormalization factor of m/(m−n). Further, the N_(eff) metric takes intoconsideration different preferential weights of the scheduler fairnessmetric for a flow. N_(eff) may be a proxy for determining how muchcompetition an incoming throughput-sensitive flow faces for access toavailable scheduler resources. In some aspects, the effective load(N_(eff)) may also account for control channel overhead.

The N_(eff) metric can be computed at the base transceiver station andforwarded to the base station controller for a network induced loadbalancing or forwarded to the AT for a device-induced load balancing. Insome aspects, the Neff metric may be computed periodically and theperiodically computed Neff metric can be filtered using a single-poleinfinite impulse response (IIR) filter of time constant equal to 500transmission units, for example. These periodic samples of N_(eff)metric from the filter can be used for the network load balancingprocess.

A base transceiver station (BTS) may retrieve the effective load metricused for network load balancing (NLB) and decide when and how totransmit the effective load metric to the base station controller (BSC).In some aspects, when a “significant enough change” in the effectiveload metric curs, the BTS may convey effective load to the BSC. In someaspects, the BTS may aggregate effective load metrics from differentsectors in a BTS, to reduce message size and frequency of transport tothe BSC.

As noted previously, effective load is transported to the base stationcontroller (BSC) or the AT from the base station transceiver (BTS). Insome aspects, the effective load can be transported from the BTS to theBSC and the BSC then aggregates the effective load values across theBTSs and transports the aggregated values to the AT. In some aspects, achange of value of N_(eff) may be used to determine when to transportN_(eff) from the BTS to the BSC. For example, N_(eff) can be transportedwhen N_(eff) is +/−X dB from the previously sent value, where X can be aselected value or a value determined based on the calculated effectiveload values.

In the example illustrated in FIG. 6, a change of N_(eff) from a valueof 4.5 dB at block 605 is translated as 5.0 dB at block 600 where X is a0.5 dB increase. Likewise, a change of N_(eff) from a value of 4.5 dB atblock 605 is translated as 4.0 dB at block 610 where X is a 0.5 dBdecrease. Any increase or decrease of 0.25 dB from the N_(eff) of 4.5 dBresults in no transportation of N_(eff) to the BSC or AT. Therefore,N_(eff) stays at block 605 where the boxes cover quarter dB units ofchange around 4.0 and 5.0 for some hysteresis. The BTS is configured todetect all N_(eff) updatable changes and transports them to the BSC. Insome aspects, the BTS uses a reliable path such as control-path, insteadof data-path, to transport sector-carrier metrics, e.g., N_(eff) fromBTS to the BSC.

The BSC receives and stores sector-carrier metrics, such as N_(eff),transported by all the sector-carriers from all the BTSs. In someaspects, a main processor may be used in the BSC that has communicationlinks with all BTSs and all BSC call processing entities as theprincipal metric-data repository or metric-database. The main processormay serve as the proxy for the whole BSC and may provide improvedbackhaul efficiency because the BTSs can send information to only onelocation. In some aspects, the main processor can be configured toaggregate N_(eff) metric across all BTSs and to cross-connectinformation across the BTSs for device or AT driven network loadbalancing, for example. The main processor may have communication linksto all call processing entities/processors within the BSC.

When long latency exists in real-time access between the BSC'scall-processing entity/processor and the main processor hosting theafore-mentioned metric-database, the metrics, e.g. N_(eff), can be madelocally available in all the call-processing processors through adatabase sync-up. The sync-up may be set to occur at a configurableperiodicity. For example, sync-up may occur when metrics change. In someaspects, the sync-up may only include changed metrics within the period,which are marshaled and updated for efficiency (i.e., no full databasedump).

The locally available storage in the call-processing BSC processors canbe within a memory module that is common for all call-processing accessand can be based on a pull model in which there is a single point ofstorage and the call processing entities get information as needed. Theinformation is not pushed to those call-processing entities that do notneed the information at the moment. The memory module can be based on asingle-write multiple-reads architecture and may use double-bufferinginstead of Semaphore protection for efficiency.

As previously discussed, server selection may be performed based on aneffective load (N_(eff)) on a sector carrier seen by an incomingthroughput-sensitive (TS) flow and based on active ATs in a sector andtheir pilot strengths or pilot signal channel quality values. Metricsrepresenting the active ATs in a sector and their pilot strengths orpilot signal channel quality values may be reported by the AT to the BSCwhen conditions change, for example. In some aspects, the BSCperiodically solicits latest pilot strength or signal channel qualityvalues reports periodically, e.g., every 4 seconds (i.e., pilot strengthupdate period). The pilot strengths of the reported pilots are thenstored by the BSC for use by the network load balancing process. In someaspects, if the solicited pilot strength report results in a change inset of sectors that the AT can receive service from, the related callprocessing is first performed, after which network load balancingprocess is executed. In some aspects, the input to the network loadbalancing process is the pilot channel quality (e.g., signal to noiseratio (SNR)). Thus, a serving sector may be selected for an AT based ona pilot signal to noise ratio (SNR) in conjunction with N_(eff). In someaspects, SNR may be computed as follows:

SNR (in dB)=(Ec/Io)/(1−Ec/Io);

where Ec/Io is the pilot strength reported by the AT to the BSC and isthe energy per chip to total received power ratio.

In a network driven network load balancing process involvingmulti-carrier AT, for example, the BSC runs the following network loadbalancing process independently for each of the carriers the AT isassigned on. In some aspects, the process is conditioned on the factthat the AT can receive service on each of the carriers from differentcells/sectors. Otherwise, the BSC may not perform network load balancingprocess for such ATs.

In some aspects, airlink or radio access technology, e.g., multi-carrierHSPA, may not allow the AT to point to different sectors acrosscarriers. In this case, even though a suitability metric can be computedseparately for each carrier, sector A in carrier 1, for example, sectorB in carrier 2, for example, may be better than the current servingsector. While the AT in some radio access technology can be served fromdifferent sectors and different carriers, in multi-carrier HSPA system,for example, the AT is served from the same sector on all the carrierseven though the suitability metric may suggest otherwise. In this case,the criteria may be based on the suitability metric in conjunction withother functions.

In some aspects, for example, multi-carrier and single-carrier LTE,where a first system may be deployed at a first bandwidth (e.g., 10 MHz)and a second system is deployed at a second bandwidth (e.g., 5 MHz) theeffective load (N_(eff)) may be normalized to the bandwidth. Forexample, if the effective load (N_(eff)) for the 10 MHz system and the 5MHz system are the same, it may be desirable or likely that that the 10MHz system is more lightly loaded and selected instead of the 5 MHzsystem.

In some aspects, the BSC determines the AT's capability to be solicitedfor pilot strength reports in order to obtain the latest values. The BSCmay run the network load balancing evaluation for an AT during an activeset change and/or N_(eff) updates. The AT may maintain a set ofcandidate sectors that can serve the AT, which may be referred to as anactive set. A BSC's call processing entity for a given AT may check forN_(eff) updates in the BSC database periodically, i.e., network loadbalancing periodicity. For example, the BSC call processing entity maycheck every 2 seconds.

In some aspects, the BSC may request pilot strength reports periodicallyfor a network load balancing candidate, and record the updated pilotstrengths. The request can be sent every four seconds, for example, anda timer can be run independently for each AT.

The execution of network load balancing processing may be distributivein nature. For example, the pilot strength request timer and networkload balancing candidate evaluation timer may be AT specific tointroduce a time-randomness in network load balancing operation acrossATs and avoid mass swings from cell/sector to cell/sector before thefeedback loop (N_(eff) update) responds.

In some aspects, the sector/cell with the highest pilot signal to noiseratio (SNR) can be among those sectors/cells that the AT is allowed toselect for service. The selection of a sector may be based on asuitability metric given by the difference between the pilot signal tonoise ratio and N_(eff) (i.e., pilot SNR−N_(eff) (dB)). For example, thesuitability metric differential may be 2 dB. At each periodic evaluationinstance, for example, the current serving sector/cell and thesector/cell with the highest suitability metric is determined.

If the pilot SNR of the current serving sector/cell and a servingcell/sector with the highest suitability metric at an evaluationinstance are below a threshold, indicating an overall poor set ofdownlinks to choose from, the AT's server selection mechanism can chooseor select across all available sectors/cells and the network may notdisallow any sector/cell. In some aspects, the current servingsector/cell can be the sector/cell with the highest suitability metricin an evaluation instance. In this case, the AT may continue to selectthe current serving sector/cell.

Otherwise, if either of the following conditions are satisfied: thehighest suitability metric exceeds that of the current servingsector/cell by a threshold value, or the pilot SNR of the currentserving sector/cell is below a threshold value then the AT can beprevented from selecting those sectors/cells having pilot channelqualities (e.g., SNRs) exceeding the pilot channel quality (e.g., SNR)of the sector/cell with the highest suitability metric. This feature canbe accomplished by implementing a feedback from those sectors/cells tothe AT indicating that the AT's selection of these sectors/cells forservice cannot be satisfied. If these conditions are not satisfied, theAT is allowed to continue selecting its current serving sector/cell.

When a delay-sensitive flow is added on any carrier, and network loadbalancing is in a mode that has excluded a subset of sectors, on thatcarrier, from selection for service by the AT, the network may notdisallow any sector/cell from being selected by the AT for service. AnAT subjected to these conditions is no longer a network load balancingcandidate on that carrier until that delay-sensitive flow is removed.

In an AT driven network load balancing process, if the BSC determinesthat a given AT supports receiving an indication from the networkcontaining relative sector load information and the AT can use thisinformation to independently implement load balancing, the BSC may notimplement a network driven network load balancing process described inthe preceding sections. Instead, if there are such ATs that support theAT driven network load balancing process in the system, the BSC maydirect the BTS to broadcast a load information message on each of itssectors. The message sent on a sector may contain its load information,as well as that of its neighbors.

The broadcast load information message may include fields such asLoadingAdjust and NeighborSectorLoadingAdjust. The LoadingAdjust fieldentails loading adjustment of a current sector and may be in units ofdecibels (dB), e.g., 0.5 dB. The NeighborSectorLoadingAdjust can be theloading adjustment of the current sector's neighbors, and may be inunits of decibels (dB), e.g., 0.5 dB.

If the AT is informed of the list of neighboring sectors in any controlmessage (that could be broadcast) from a sector before it connects forservice with the network, the network and the AT can thereafter agree topair up the ordered listing of NeighborSectorLoadingAdjust fields inthis load information message with the ordered listing of neighbors inthe aforementioned control message. This can reduce the messageoverheads in periodic over the air transmission by avoiding a neighborsector identifier associated with the LoadingAdjust.

The LoadingAdjust and NeighborSectorLoadingAdjust can be populated asfollows:

Let sectors s1, s2, . . . , si, . . . , sN map to N_(eff) _(—) 1,N_(eff) _(—) 2, . . . , N_(eff) _(—) i, . . . N_(eff) _(—) N.

Let sector sr have the least N_(eff)N_(eff) _(—) r=min(N_(eff) _(—) i,for all i from 1 to N)

LoadingAdjust for sector si=10*log 10(N_(eff) _(—) i/N_(eff) _(—) r)

The BSC may forward the LoadingAdjust values for the given sector andits neighbors to the BTS. The BSC receives the N_(eff) metric frommultiple BTS's as explained earlier in the context of network drivennetwork load balancing. The BSC periodically updates each BTS with theinformation to set the LoadingAdjust values in the LoadInformationmessage for that BTS's sectors, and its neighbors, captured in theinterval since the previous update. The BTS may sequence theNeighborSectorLoadAdjust and may update values in the nextLoadInformation message transmitted. The BTS may also transmit theLoadInformation message in a broadcast control packet.

The load information message may be a lower priority message and may besent if other higher priority messages together with the loadinformation message do not increase the message size to require extraquanta of message packets. The load information message may be targetedfor ATs that are in connection, and not in sleep mode. Those ATs thatare in sleep mode, and wake up to listen to control transmissions fromthe network may not be requested to stay awake longer than typicallyneeded, just to receive this message, which would be superfluous for theAT in that state.

FIG. 2 is a block diagram illustrating a method or process for loadbalancing in a wireless network. The process begins at block 202 wherethe effective load values for sectors accessible to an access terminalof the wireless network is received. The effective load values mayrepresent effective loads on the sectors. At block 204, pilot signalchannel quality values of the sectors are received. Finally, at block206, a serving sector is selected, from the sectors, for the accessterminal based on the effective load values and the pilot signal channelquality values.

FIG. 3 is a block diagram illustrating a method or process forcommunicating in a wireless network. The process begins at block 302where effective load values at an access terminal for accessible sectorsof the wireless network are received. The effective load values mayrepresent effective loads on the sectors. At block 304, pilot signalchannel quality values of the accessible sectors are identified.Finally, at block 306 a serving sector is selected, from the accessiblesectors, for the access terminal based on the effective load values andthe pilot signal channel quality values.

In one configuration, the eNodeB 110 or BSC 530 is configured forwireless communication including means for receiving effective loadvalues for sectors accessible to an access terminal of the wirelessnetwork. In one aspect, the receiving means may be the controllerprocessor 440 and memory 442, the receive processor 438, demodulators432 a-432 t and antenna 434 a-t configured to perform the functionsrecited by the receiving means. The eNodeB 110 or BSC 530 is alsoconfigured to include a means for receiving pilot signal channel qualityvalues of the sectors. In one aspect, the receiving means may be thecontroller processor 440 and memory 442, the receive processor 438,demodulators 432 a-432 t and antenna 434 a-t configured to perform thefunctions recited by the receiving means. The eNodeB 110 or BSC 530 isalso configured to include a means for selecting a serving sector, forthe access terminal based on the effective load values and the pilotsignal channel quality values. In one aspect, the selecting means may bethe controller processor 440 and memory 442 configured to perform thefunctions recited by the selecting means. In another aspect, theaforementioned means may be a module or any apparatus configured toperform the functions recited by the aforementioned means.

In one configuration, the UE 120 or AT 520 is configured for wirelesscommunication including means for receiving effective load values at anaccess terminal for accessible sectors of the wireless network. In oneaspect, the receiving means may be the controller/processor 480, andmemory 482, the receive processor 458, demodulators 454 a-454 r andantenna 452 a-r configured to perform the functions recited by thereceiving means. The UE 120 or AT 520 is also configured to include ameans for identifying pilot signal channel quality values of theaccessible sectors. In one aspect, the identifying means may be thecontroller/processor 480, and memory 482 configured to perform thefunctions recited by the identifying means. The UE 120 or AT 520 is alsoconfigured to include a means for selecting a serving sector, for theaccess terminal based on the effective load values and the pilot signalchannel quality values. In one aspect, the selecting means may be thecontroller/processor 480, and memory 482 configured to perform thefunctions recited by the selecting means. In another aspect, theaforementioned means may be a module or any apparatus configured toperform the functions recited by the aforementioned means.

Those of skill would further appreciate that the various illustrativelogical blocks, modules, circuits, and algorithm steps described inconnection with the disclosure herein may be implemented as electronichardware, computer software, or combinations of both. To clearlyillustrate this interchangeability of hardware and software, variousillustrative components, blocks, modules, circuits, and steps have beendescribed above generally in terms of their functionality. Whether suchfunctionality is implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem. Skilled artisans may implement the described functionality invarying ways for each particular application, but such implementationdecisions should not be interpreted as causing a departure from thescope of the present disclosure.

The various illustrative logical blocks, modules, and circuits describedin connection with the disclosure herein may be implemented or performedwith a general-purpose processor, a digital signal processor (DSP), anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA) or other programmable logic device, discrete gate ortransistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described herein. Ageneral-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with thedisclosure herein may be embodied directly in hardware, in a softwaremodule executed by a processor, or in a combination of the two. Asoftware module may reside in RAM memory, flash memory, ROM memory,EPROM memory, EEPROM memory, registers, hard disk, a removable disk, aCD-ROM, or any other form of storage medium known in the art. Anexemplary storage medium is coupled to the processor such that theprocessor can read information from, and write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor. The processor and the storage medium may reside in anASIC. The ASIC may reside in a user terminal. In the alternative, theprocessor and the storage medium may reside as discrete components in auser terminal.

In one or more exemplary designs, the functions described may beimplemented in hardware, software, firmware, or any combination thereof.If implemented in software, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium. Computer-readable media includes both computerstorage media and communication media including any medium thatfacilitates transfer of a computer program from one place to another. Astorage media may be any available media that can be accessed by ageneral purpose or special purpose computer. By way of example, and notlimitation, such computer-readable media can comprise RAM, ROM, EEPROM,CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium that can be used to carryor store desired program code means in the form of instructions or datastructures and that can be accessed by a general-purpose orspecial-purpose computer, or a general-purpose or special-purposeprocessor. Also, any connection is properly termed a computer-readablemedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), or wireless technologiessuch as infrared, radio, and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL, or wireless technologies such asinfrared, radio, and microwave are included in the definition of medium.Disk and disc, as used herein, includes compact disc (CD), laser disc,optical disc, digital versatile disc (DVD), floppy disk and blu-ray discwhere disks usually reproduce data magnetically, while discs reproducedata optically with lasers. Combinations of the above should also beincluded within the scope of computer-readable media.

The previous description of the disclosure is provided to enable anyperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the spirit or scopeof the disclosure. Thus, the disclosure is not intended to be limited tothe examples and designs described herein but is to be accorded thewidest scope consistent with the principles and novel features disclosedherein.

1. A method of communicating in a wireless network, comprising:receiving effective load values for a plurality of sectors accessible toan access terminal of the wireless network, the effective load valuesrepresenting effective loads on the plurality of sectors; receivingpilot signal channel quality values of the plurality of sectors; andselecting a serving sector, from the plurality of sectors, for theaccess terminal based on the effective load values and the pilot signalchannel quality values.
 2. The method of claim 1, in which an effectiveload value of the effective load values is determined based on at leastone of a number of existing throughput sensitive (TS)-flows in a sectorof the plurality of sectors that compete for scheduler resources.
 3. Themethod of claim 1, in which selecting comprises: for each of theplurality of sectors for which an effective load value is received,determining a suitability metric by subtracting an effective load valuefor each sector from a pilot signal channel quality of each sector; andselecting a sector with a highest suitability metric.
 4. The method ofclaim 3, further comprising computing the effective load values and thesuitability metric for each carrier of a multi-carrier configuration ofthe access terminal.
 5. The method of claim 1, further comprisingreceiving a current effective load value of the effective load valueswhen a difference between the current effective load value and a prioreffective load value meets a threshold value.
 6. The method of claim 1,in which the receiving, receiving and selecting are implementedindependently for each carrier of a multi-carrier configuration of theaccess terminal.
 7. A method of communicating in a wireless network,comprising: receiving effective load values at an access terminal for aplurality of accessible sectors of the wireless network, the effectiveload values representing effective loads on the sectors; identifyingpilot signal channel quality values of the plurality of accessiblesectors; and selecting a serving sector, from the plurality ofaccessible sectors, for the access terminal based on the effective loadvalues and the pilot signal channel quality values.
 8. The method ofclaim 7, in which an effective load value of the effective load valuesis determined by at least one of a number of existing throughputsensitive (TS)-flows in a sector of the plurality of accessible sectorsthat compete for scheduler time and scheduler resources.
 9. The methodof claim 7, in which selecting comprises: for each of the a plurality ofaccessible sectors for which an effective load is received, determininga suitability metric by subtracting an effective load value for eachsector from a pilot signal channel quality of each sector; and selectinga sector with a highest suitability metric.
 10. The method of claim 7,further comprising receiving loading adjustment information of a sectorrepresented by a ratio of the effective load of the sector to that of asector with a least effective load; and selecting the serving sector,from the plurality of accessible sectors, for the access terminal basedat least in part on the loading adjustment information.
 11. An apparatusfor communicating in a wireless network, comprising: means for receivingeffective load values for a plurality of sectors accessible to an accessterminal of the wireless network, the effective load values representingeffective loads on the plurality of sectors; means for receiving pilotsignal channel quality values of the plurality of sectors; and means forselecting a serving sector, from the plurality of sectors, for theaccess terminal based on the effective load values and the pilot signalchannel quality values.
 12. An apparatus for communicating in a wirelessnetwork, comprising: means for receiving effective load values at anaccess terminal for a plurality of accessible sectors of the wirelessnetwork, the effective load values representing effective loads on thesectors; means for identifying pilot signal channel quality values ofthe plurality of accessible sectors; and means for selecting a servingsector, from the plurality of accessible sectors, for the accessterminal based on the effective load values and the pilot signal channelquality values.
 13. An apparatus for communicating in a wirelessnetwork, comprising: a memory; and at least one processor coupled to thememory and configured: to receive effective load values for a pluralityof sectors accessible to an access terminal of the wireless network, theeffective load values representing effective loads on the plurality ofsectors; to receive pilot signal channel quality values of the pluralityof sectors; and to select a serving sector, from the plurality ofsectors, for the access terminal based on the effective load values andthe pilot signal channel quality values.
 14. The apparatus of claim 13,in which the at least one processor determines an effective load valueof the effective load values based on at least one of a number ofexisting throughput sensitive (TS)-flows in a sector of the plurality ofsectors that compete for scheduler resources.
 15. The apparatus of claim13, in which the at least one processor is further configured to selecta serving sector by: for each of the plurality of sectors for which aneffective load value is received, determining a suitability metric bysubtracting an effective load value for each sector from a pilot signalchannel quality of each sector; and selecting a sector with a highestsuitability metric.
 16. The apparatus of claim 15, in which the at leastone processor is further configured to compute the effective load valuesand the suitability metric for each carrier of a multi-carrierconfiguration of the access terminal.
 17. The apparatus of claim 13, inwhich the at least one processor is further configured to receive acurrent effective load value of the effective load values when adifference between the current effective load value and a prioreffective load value meets a threshold value.
 18. The apparatus of claim13, in which the at least one processor is further configured to receiveeffective load values, to receive pilot signal channel quality valuesand to select a serving sector independently for each carrier of amulti-carrier configuration of the access terminal.
 19. An apparatus forcommunicating in a wireless network, comprising: a memory; and at leastone processor coupled to the memory and configured: to receive effectiveload values at an access terminal for a plurality of accessible sectorsof the wireless network, the effective load values representingeffective loads on the sectors; to identify pilot signal channel qualityvalues of the plurality of accessible sectors; and to select a servingsector, from the plurality of the plurality of accessible sectors, forthe access terminal based on the effective load values and the pilotsignal channel quality values.
 20. The apparatus of claim 19, in whichthe at least one processor is further configured to determine aneffective load value of the effective load values based on at least oneof a number of existing throughput sensitive (TS)-flows in a sector ofthe plurality of accessible sectors that compete for scheduler time andscheduler resources.
 21. The apparatus of claim 19, in which the atleast one processor is further configured to select a serving sector by:for each of the a plurality of accessible sectors for which an effectiveload is received, determining a suitability metric by subtracting aneffective load value for each sector from a pilot signal channel qualityof each sector; and selecting a sector with a highest suitabilitymetric.
 22. The apparatus of claim 19, in which the at least oneprocessor is further configured: to receive loading adjustmentinformation of a sector represented by a ratio of the effective load ofthe sector to that of a sector with a least effective load; and toselect the serving sector, from the plurality of accessible sectors, forthe access terminal based at least in part on the loading adjustmentinformation.
 23. A computer program product for wireless communicationsin a wireless network, comprising: a computer-readable medium havingnon-transitory program code recorded thereon, the program codecomprising: program code to receive effective load values for aplurality of sectors accessible to an access terminal of the wirelessnetwork, the effective load values representing effective loads on theplurality of sectors; program code to receive pilot signal channelquality values of the plurality of sectors; and program code to select aserving sector, from the plurality of sectors, for the access terminalbased on the effective load values and the pilot signal channel qualityvalues.
 24. A computer program product for wireless communications in awireless network, comprising: a computer-readable medium havingnon-transitory program code recorded thereon, the program codecomprising: program code to receive effective load values at an accessterminal for a plurality of accessible sectors of the wireless network,the effective load values representing effective loads on the sectors;program code to identify pilot signal channel quality values of theplurality of accessible sectors; and program code to select a servingsector, from the plurality of the plurality of accessible sectors, forthe access terminal based on the effective load values and the pilotsignal channel quality values.